I got a weird one here, so I don't expect an exact answer, but more of a pointer in the right direction:
I'm working on a site and everything works as expected on my local server, but when I move it to staging server, images in a file Matrix column don't "stick" so to speak. When I create the entry, everything is normal, it actually seems to populate the DB since the entry appears on the site just fine, including the images, but when I go back and try to edit that same entry, the images are gone from the Matrix field (and not from plain old file fields). If I save the entry again, the images don't show up anymore on the site so it's not a problem of thumbnails not showing up on the publish page… Matrix seems to not be able to tell that images are in that field and they show up as empty on the publish page even though the images show up on the site.
The only difference I can think of is the server's setup. My local MAMP which works fine runs PHP 5.3.14. The server where Matrix doesn't work runs PHP 5.4.8.
The site runs on EE v2.3.1 + Matrix 22.214.171.124
As I mentioned before, any pointer in the right direction would be more than enough. I just don't even know where to start to troubleshoot… Thanks!